The development of ruthenium olefin metathesis catalysts has firmly established olefin metathesis as a versatile and reliable synthetic technique for organic syntheses. The exceptionally wide scope of substrates and functional group tolerance makes olefin metathesis a valuable technique. In this application, the use of olefin metathesis to produce functionalized polymers is an example of the usefulness and the robustness of olefin metathesis technology. Compared to traditional synthetic organic techniques, olefin metathesis efficiently produces compounds and polymers that are otherwise hard to synthesize. Numerous hours of research have resulted in the elucidation of many olefin metathesis reactions catalyzed by various transition metal complexes. In particular, certain ruthenium and osmium carbene compounds, known as “Grubbs' catalysts,” have been identified as effective catalysts for olefin metathesis reactions such as, for example, cross-metathesis (CM), ring-closing metathesis (RCM), ring-opening metathesis (ROM), ring opening cross metathesis (ROCM), ring-opening metathesis polymerization (ROMP) or acyclic diene metathesis (ADMET) polymerization.
Various methods of preparing telechelic polymers have been developed and disclosed in the art, in large part due to the continuing interest in preparing macromolecular materials through the reactive functional groups present at the chain termini of such polymers. For example, telechelic polymers have found use in a number of applications, including the synthesis of block and star polymers, and crosslinked and ionic polymer networks. Low molecular weight telechelic polymers have also been prepared for use in reaction molding systems, block copolymer formation, and in the development of thermoplastic elastomer and urethane systems.
Although many different types of functional end groups have potential utility, hydroxyl-functional telechelics have, by far, achieved the most commercial application. Hydroxyl-end functionalized telechelics synthesized via ROMP with chain transfer agents (CTAs) are disclosed in Chung et. al. (U.S. Pat. No. 5,247,023), Grubbs, et. al. (U.S. Pat. No. 5,750,815) and Nubel, et al (U.S. Pat. Nos. 5,512,635, 5,559,190, 5,519,101 and 5,403,904). However, these hydroxyl-functional telechelics were synthesized via multi-step processes since protected diol CTAs (e.g., 1,4-diacetoxy-2-butene) were required to provide reasonable yields of polymers which then had to be deprotected to yield the desired hydroxy-functional materials. As an example, the attempted but unsuccessful use of 2-butene-1,4-diol as a CTA for forming telechelic polymers has also been reported in J. Am. Chem. Soc. 2003, 125, 8515-8522. Direct ROMP synthesis of hydroxy-telechelic polymers have been disclosed by Peters (U.S. Pat. No. 6,476,167) via the use of unsaturated polyether diol CTAs derived from the reaction product of unsaturated dihydric alcohols and alkylene oxides. Aside from the difficulties in purifying and characterizing such oligomeric CTAs, their polar nature may potentially lead to phase incompatibilities with many desired cycloalkene comonomers, and may diminish chemical resistance of the ultimate telechelics and/or downstream polymers synthesized therefrom.
Despite the advances achieved in preparing telechelic polymers via ROMP, a continuing need exists for the direct synthesis of hydroxyl-functionalized telechelic polymers from practical hydroxyl-functionalized CTAs. Of particular interest are systems that utilize materials derived from renewable feedstocks, in addition to allowing for the improved incorporation of functional groups in such telechelic polymers.